DISPERSAL BY BIRDS AND ANTS 413 



{a) In the whin, broom, violet, and others the elaiosome 

 is arillar. 



{h) The basal part of the fruit wall is differentiated as an 

 elaiosome in Fumaria and Anemone hepatica. 



(c) The basal part of the calyx forms the elaiosome in 

 Parietaria lusitanica. 



(d) Part of the floral axis forms the elaiosome in Ajuga 

 and other Labiatae, and in some Scrophulariaceae. 



(e) A part of the peduncle functions as elaiosome in 

 Aremonia agrimonioides and Thesium alpinum. 



( / ) In Car ex digitata and other Carices the elaiosome is 

 bracteal. 



{g) In Melica nutans and other grasses the elaiosome is 

 derived from the inflorescence axis. 



(/;) In Allium and many other monocotyledons the 

 thin outer seed coat is impregnated with oil. 



Observations on a large number of seeds and fruits 

 showed that they were vigorously sought for by ants ; seeds 

 from which the elaiosome had been removed were, on the 

 whole, selected less frequently. Transport for a distance 

 of over 70 yds. was observed. Sernander holds that car- 

 riage for a small distance from the parent plant is the most 

 important result of dispersal by ants. Plants with ant- 

 dispersed seeds are most numerous in woods, where the 

 bare soil allows the ants freer movement. In the vegetation 

 of a Swedish water meadow, out of 32 species 2, or 6 per 

 cent., were ant- dispersed, while in a neighbouring wood 

 there were 9 out of 35, or 25 per cent. The importance of 

 clear soil is strikingly illustrated by an observation on the 

 dispersal of whin seeds on an English heath by Weiss (1908). 

 The seedlings sprouted only along the margins of tracks 

 on the bare soil of which the ants could move, never among 

 the vegetation. 



Ant-dispersal leads us to dispersal by birds or mammals, 

 which carry seeds and fruits sticking on their feathers and 

 fur. The fruits of Galium aparine, the goose-grass, are 

 provided with many small hooks which readily become firmly 

 attached to the fur of passing rabbits and sheep. The bracts 



